错误处理

• catchErrorJustReturn

  当遇到 error 事件的时候，就返回指定的值，然后结束

let sequenceThatFails = PublishSubject()
 
sequenceThatFails
    .catchErrorJustReturn("错误")
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)
 
sequenceThatFails.onNext("a")
sequenceThatFails.onNext("b")
sequenceThatFails.onNext("c")
sequenceThatFails.onError(MyError.A)
sequenceThatFails.onNext("d")

• catchError

  该方法可以捕获 error，并对其进行处理
  同时还能返回另一个 Observable 序列进行订阅（切换到新的序列）

let sequenceThatFails = PublishSubject()
let recoverySequence = Observable.of("1", "2", "3")
 
sequenceThatFails
    .catchError {
        print("Error:", $0)
        return recoverySequence
    }
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)
 
sequenceThatFails.onNext("a")
sequenceThatFails.onNext("b")
sequenceThatFails.onNext("c")
sequenceThatFails.onError(MyError.A)
sequenceThatFails.onNext("d")

• retry

  使用该方法当遇到错误的时候，会重新订阅该序列。比如遇到网络请求失败时，可以进行重新连接
  retry() 方法可以传入数字表示重试次数。不传的话只会重试一次

var count = 1
        
let sequenceThatErrors = Observable.create { observer in
    observer.onNext("a")
    observer.onNext("b")
            
    //让第一个订阅时发生错误
    if count == 1 {
        observer.onError(MyError.A)
        print("Error encountered")
        count += 1
    }
            
    observer.onNext("c")
    observer.onNext("d")
    observer.onCompleted()
            
    return Disposables.create()
}
        
sequenceThatErrors
    .retry(2)  //重试2次（参数为空则只重试一次）
    .subscribe(onNext: { print($0) })
    .disposed(by: disposeBag)

参考文章：Swift - RxSwift的使用详解15（错误处理）